HwyStarJoe

I searched but couldn't find the data I was looking for. Maybe I missed it.

I'm troubleshooting what amounts to a miss. ScanXL shows random misses, but it's a constant miss somewhere.
The engine is an '06 GTO LS2\automatic. Original harness for both that were never removed. All else is stock as well. E40 ECM.

All the header tubes are hot. New plugs, all the plug wires are the same resistance... 750kOhms or so. Injectors cleaned and all flow the same. I didn't put them back in the same ports when I got them back. I haven't pulled the valve covers or intake yet.

I pulled the connector on each coil one at a time to see if it'd run differently and I couldn't detect any change in how it ran. Strange. I didn't do that for the injectors yet.

I have (and know how to use) an oscilloscope. What I don't know is what type of waveform I'm supposed to be looking for at the coils, and then at the injectors? I saw that data somewhere but I can't find it now. If I can rule out the signals from the ECM, I can get closer to a diagnosis. I would take it to New Era but I'm not paying $80\hr labor when I'm perfectly capable of diagnosing it (and fixing it) myself. I want to get it on the dyno there but don't want to get kicked out when they find how poorly its running. I realize it could be the tune that fixes it, but want to rule wiring\ECM out first.

Thanks for any help!

01cherryreds10

iTrader: (9)

I never really got into those scopes, is there anyway you can get a tech 2 onto it and see which cylinder is misfiring with the misfire graphic function? The scope is kind of a dieing tool to use seems like only old school teachers use it just to show students

bczee

iTrader: (12)

I was chasing a miss for a month or more... no DTC, nothing looked bad on monitoring real time in the O2 voltages, STF & LTF percentages where moving as the should, checked and double checked wires, connectors, wapped plug wires, coild and injectors. Still had radom miss. Did compression and leak down test. Checked rockers and push rods...

After weeks of trying to find what was causing the miss. It turned out to be a hair line crack one one plug. Checking the plugs, they all looked good and the same color... so I discountet that it was the plugs after checking them twice.. third time was the charm !

so.. sugguestion is to try chaging the plug(s).

good luck.

BC

HwyStarJoe

Well, unless I cracked a plug installing them a couple weeks ago, it still runs exactly how it did before changing them.

I do have what looks like a LTFT problem, but I think it's due to inconsistent data from the ECM. Would a faulty O2 sensor cause these issues, or would a bad sensor cause the engine to run so bad I wouldn't be able to drive it? I drive it everyday and it runs fine except for the "miss". It's as if one cylinder has a problem, not something across the board.

gofastwclass

iTrader: (2)

A misfire will make your fuel trims crazy.

I didn't see it listed, have you done a compression check or checked the rockers, springs and pushrods? If it's an engine from a GTO someone could have bounced it off the limiter a few too many times and bent a valve having some fun.

I simply can't underestimate the power of a high quality scan tool with any fuel injected engine. By "high quality" I don't mean a simple $99 code reader, I mean something that can monitor and log the live data stream generated by the PCM. This is even better if you can play it back later and see it graphically.

HwyStarJoe

Other than the plugs and injectors, I haven't done anything to it.
I thought about the last owner banging the limiter too. I guess before I scratch my head on it anymore externally, I'll pop the covers and intake. Wanted to avoid that but it is what it is.
I have scan software... But I seem to be having trouble collecting all the data on Bank 2 for some reason. I get a lit of dead readings. Bank 1 reads, records and updates fine.

Thanks all.